Check engine light P0300 and P0442, but at the same time.

[Rjones2478]

I have a 98 Ford Explorer. The check engine light came on recently. I took the car to AutoZone and had it scanned. Code P0300 appeared and I receved the print out explaining the code and possible solutions. I then proceded to my mechanic's shop, he scanned the car and code P0442 came up. Is there a relation between the two codes? I know P300 indicates a random misfire vs. P442 indicating an emission leak; but why did I receive to diffrent reading within an hours time? Because with either reading wouldn't both codes have came up if they both were both an issue?

 

[BobWiersema]

The 442 code will not set the CEL so the first guy just probably didnt notice it.
The misfire code is probably being caused by the 442 code (small fuel vapor leak).
Below is some help from obd-codes.com

What does that mean?

This indicates a fuel vapor leak in the EVAP control system. It means a very small leak has been detected. In fact, the leak can be from a hole as small as 0.04" in diameter. The (EVAP) emission control system prevents the escape of fuel vapors from a vehicle's fuel system. Fuel vapors are routed by hoses to a charcoal canister for storage. Later, when the engine is running a purge control valve opens allowing intake vacuum to siphon the fuel vapors into the engine.

Causes

A code P0442 most likely means one or more of the following has happened:

* A loose or improperly affixed gas cap
* A non-conforming gas cap (i.e. not factory/original brand)
* A small leak/hole in a fuel vapor hose/tube
* Other small leak in EVAP system
* Faulty vent o-ring seal

Possible Solutions

With a P0442, the most common repair is to:

* Remove and reinstall the gas cap, clear the codes, and drive for a day and see if the codes come back.
* Otherwise, replace the gas cap, or
* Inspect the EVAP system for cuts/holes in tubes/hoses


Direct link http://www.obd-codes.com/p0442

 

[Sams01XplrSprt]

welcome

 

[Rjones2478]

Thank you for the explaination and the response Bob, now I feel alittle better about bringin the truck back to the mechanic. I took the truck in to him 2 weeks ago for a new oil pan and he charged me $350.00. The cost knocked me back bit and I just want to know as much as possible before I go back to him.

Sam, Thank you for the warm welcome.


RJ

 

[BrooklynBay]

Welcome to this forum! I've moved your thread into the EEC-V section.